1. Field of the Invention
Aspects of the present invention relate to a contact probe, a probe socket, an electrical characteristic measuring device, and a method for pushing the contact probe against an object to be measured. More particularly, an aspect of the present invention relates to a technology which makes it possible to mitigate electrostatic discharge damage or mechanical damage to an electronic device when measuring electrical characteristics of the electronic device.
2. Description of the Related Art
As shown in FIG. 14, a related electrical characteristic measuring device, such as a digital multimeter, comprises a body 61 incorporating an electrical measuring unit, a measurement cable 62 drawn out from the body 61, and a probe socket 63 connected to the measurement cable 62. In the example shown in FIG. 14, the probe socket 63 has two contact probes 64. By pushing the contact probes 64 against, for example, terminals T1 and T2 of a thin-film magnetic head H (object to be measured), an electrical characteristic between the terminals T1 and T2 can be measured.
In the related electrical characteristic measuring device shown in FIG. 14, the measurement cable 62 may accumulate electrical charge because it has an insulating film, and the contact probes 64 are in an easily chargeable state because they are in electrically floated states from a power source ground of the body 61. When the measurement cable 62 or the contact probes 64 are charged, and the contact probes 64 contact the terminals T1 and T2 of the thin-film magnetic head H, an electrical charge Q moves momentarily. Even if the electrical charge Q that moves momentarily is a small amount, a current value, which is a time differential of the electrical charge Q, is increased. The flow of a large amount of current causes electrostatic discharge damage to the thin-film magnetic head H.
Contact probes having barrel structures are disclosed as means for preventing electrostatic discharge damage in, for example, Japanese Unexamined Patent Application Publication No. 2001-201515. Probes having the same structures as the contact probes disclosed in Japanese Unexamined Patent Application Publication No. 2001-201515 is shown in FIG. 15. As shown in FIG. 15, contact probes 200 have respective probe pins 201 and respective springs 202 disposed in respective barrels 203. The probe pins 201 are biased towards respective ends 203a of the barrels by the respective springs 202. Ends of the probe pins 201 protrude from the respective barrels 203. The probe pins 201 are formed of high-resistance materials, and the barrels 203 are formed of low-resistance materials.
When the above-described contact probes are pushed against the respective terminals T1 and T2 of the thin-film magnetic head H, first, ends of the probe pins 201 come into contact with the respective terminals T1 and T2 of the thin-film magnetic head. Then, the probe pins 201 push and compress the springs 202, and are pushed into the respective barrels 203. At the same time that the probe pins 201 are pushed into the respective barrels 203, the ends 203a of the barrels 203 come into contact with the respective terminals T1 and T2. As a result of the barrels 203 coming into contact with the respective terminals T1 and T2, an electrical circuit is formed between the thin-film magnetic head H and the electrical characteristic measuring device, and an electrical characteristic between the terminals T1 and T2 of the thin-film magnetic head H is measured.
When the ends of the respective probe pins 201 contact the respective terminals T1 and T2 of the thin-film magnetic head, electrical charges flow between the thin-film magnetic head H and the probe pins 201. Since the probe pins 201 are formed of high-resistance materials, the electrical current value at this time is low. Accordingly, since the electrical charges flow with a small current value, and are removed before the barrels 203 and 203 come into contact with their respective terminals T1 and T2, it is possible to prevent electrostatic discharge damage.
However, since the contact probes disclosed in Japanese Unexamined Patent Application Publication No. 2001-201515 are directly mounted to the probe socket, they are formed so that force applied to the probe socket is directly applied to the contact probes. Therefore, when the probe socket is strongly pushed against the terminals of the thin-film magnetic head, the ends of the barrels strongly contact the terminal surfaces, thereby producing contact pressure which may damage the terminal surfaces.
In addition, as shown in FIG. 16, the positions of terminal surfaces T11 and T22 of the thin-film magnetic head may not be aligned because of stacking of dimensional tolerance at the time of manufacture. When one tries to measure electrical characteristics by pushing the probe socket 63 against the non-aligned terminals T1 and T2, and the barrel end 203a of one of the contact probes 200 contacts the terminal surface T11, only the probe pin 201 of the other contact probe 200 may be in contact with the terminal surface T22. In this case, the probe pin 201 having high resistance is interposed in a measurement circuit system, thereby preventing precise measurements of the electrical characteristics.